This invention relates in general to lock devices and deals more specifically with an automatically acting lock device for holding a dump-type truck body.
Dump trucks and similar vehicles having tiltable bodies are used in a wide variety of applications, including the carrying of livestock and other loads which tend to shift considerably during transport. To prevent accidental raising of the truck body and other adverse consequences caused by shifting of such loads, it is common for the body to be manually locked to the truck frame after the power cylinder has been retracted to lower the body to the load carrying position. Although lock devices of this type hold down the dump body satisfactorily, it is necessary to lock them manually and also to release them manually when the contents are to be unloaded. Not only does this procedure require time and inconvenience, it is not uncommon for the operator to neglect to activate the lock at times, thereby leaving the truck body free to accidently raise under the influence of shifting loads and other forces. Moreover, manual hold downs wear out or become misadjusted so that the truck body is loose and can bounce and jar on the frame, causing abrasion and undue wear on both the truck body and the frame.
While self acting automatic type locks have been proposed, they have not met with success for a variety of reasons. The main drawback of such locks is that they are so complicated and expensive as to make them impractical in most applications. Furthermore, this type of device is difficult to install, and it is not well suited for use with all of the various styles of truck bodies and the various hoists that are used. The self acting locks that have been proposed are also susceptible to accidental release, particularly after they have been subjected to the wear that accompanies prolonged use.
Another approach that has been taken is to utilize a double acting hydraulic cylinder which maintains the truck body down by means of hydraulic pressure. Even though this approach has met with a measure of acceptance, it has not been entirely satisfactory in all respects. Most notably, it is often not practical to incur the increased cost of the double acting cylinder as compared to the more economical single acting cylinder. In any event, the need for a double acting cylinder adds significantly to the overall cost and complexity of the dump mechanism. In addition, it is necessary to maintain continuous hydraulic pressure during transport, and failure of the hydraulic system or loss of pressure for any reason releases the truck body, possibly at an inopportune time. The same problems exist for all lock devices which rely on fluid pressure for their operation. When the joints are worn or improperly adjusted, the double acting cylinder is unable to hold down the truck body tightly enough to prevent bouncing and jarring and the accompanying damage to the bed and truck frame.
In view of these and other difficulties in existing lock device, it is the principal goal of the present invention to provide an improved automatically acting lock device for dump-type truck bodies.
More specifically, it is an object of the invention to provide a lock device which automatically locks when the truck body is lowered and which automatically releases when the power cylinder is activated to raise the body. Consequently, the possibility of human error is eliminated, as is the time and inconvenience associated with the manually operated locks currently in widespread use.
Another object of the invention is to provide a lock device of the character described that is readily adapted for use with truck bodies of virtually any size and construction.
Still another object of the invention is to provide a lock device of the character described that may be used with various types of hoists and dumping mechanisms.
An additional object of the invention is to provide a lock device of the character described which operates by means of a mechanical linkage that does not rely on fluid pressure to hold the dump body.
A further object of the invention is to provide a lock device of the character described which is constructed simply and economically and which operates reliably even after extensive use.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.